I have heard that Bayern Munich are interested in Kai Havertz as a summer transfer target. Tuchel must be wishing to reunite with him and maybe Havertz would also lean towards a potential deal.
Kai Havertz is good enough when Tuchel was still managing Chelsea, but in this season he's not really good striker. I think there's a big possibility Havertz will accept it because he's a German and he will get many trophies since Bayern Munich is usually become a champion in Bundesliga, also they will always get a slot for Champions League.
As much as they still all want Lionel Messi return when it's not really as smart as it seems even if he returns, he shouldn't be used for attacking options but rather for the attacking midfielder position.
Despite he's play at center forward position in PSG, Messi is playing like as a central midfielder where he will depends to Mbappe and Neymar as the finishers. But I don't expect Messi will return to Barcelona since Barcelona can't afford the current Messi's salary in PSG.